In the early Eocene period, a small horse (Eohippus) accidentally dies in the depths of a lake. Over time, the body of the mare decays. Heat and pressure convert the remains of the animal into oil. Thousands of feet beneath the surface of Utah and millions of years later, that oil is tapped. As it travels through a pipeline, a nearby worker is injured. As a result of the accident, the man loses part of his arm.

The worker, Djamolidine Hasanov, was born in Azerbaijan. Before coming to the United States, he changed his name to Jimmy Nash. As a boy, he loved to bicycle. As an adult in America, his pastimes include drinking beer and writing haiku. After he is injured at work, Jimmy becomes a drifter and lives off his disability benefits.

The oil derived from the matter of the prehistoric horse continues its journey through time and space. It is refined into gasoline and transported to a gas station in Austin, Texas. On June 23, 1975, some of that gasoline is pumped into the tank of a Ford Pinto. One drop of the fuel comes from the once-pumping heart of the ancient equine.

The car is driven by Clarissa Sanders, a college student who is enthralled by biology and genetics. Later that day, she picks up a hitchhiker on a highway leading to San Antonio. The man has an accent and is missing his lower right arm. Jimmy Nash shares some LSD with Clarissa. He even drives her automobile. On the same day, Clarissa inhales some soot particles emitted in the car's exhaust fumes. They contain a carcinogen - benzapyrene. Thirty years later, she is diagnosed with metastatic adenocarcinoma of the lung. Three months after receiving the diagnosis, Clarissa dies.